Sell hair, plasma, or other body parts/fluids. Long, healthy, untreated hair can be sold for a variety of purposes (including high-end wig- and extension-making) and earn you anywhere from several hundred to several thousand dollars depending on color, health, and length. Plasma can be “donated” (for compensation) provided that you are old, healthy, and heavy enough to qualify. Sperm can be donated, but you usually have to know (and be able to document) a fair amount of information about your parents as well as your medical history to be eligible. But be wary; for example, donating eggs is often touted as a fast, high-profit medical procedure, but the process is actually requires that the participant undergo hormonal and medical treatment, receive regular checkups and ultrasounds, and abstain from sex and intoxicants, all of which take weeks or even months before the eggs are even eligible for removal. The removal process itself is invasive and lasts about 30 minutes.[2] Consider your options very carefully before taking on anything like this.

Get paid for your opinions. Taking surveys online can be a relatively quick way to earn enough to afford a few extras. Harris Poll Online, for example, awards points for the completion of online surveys, which can take between five and 25 minutes to fill out. Survey takers accumulate points and can redeem them for gift cards from retailers such as Amazon and Starbucks. Other online outfits that will pay you to take surveys include SurveyClub, Global Test Market and Swagbucks. There's no cost to sign up.
You'll have to leave your house for this one, but hospitality consulting firms like Coyle rely on secret shoppers to evaluate their clients' services. Sign up to be an evaluator and you could get paid to receive spa treatments, dine at restaurants or stay at a hotel. There are lots of opportunities in other fields, too, ranging from entertainment (hello, amusement parks!) to automobiles. However, watch out for scams; check the MSPA for a list of legitimate mystery shopping companies. Earning potential: About $10 per hour
I recently stumbled on the Trim app and I have to say, this one is a game changer. It’s a simple app that acts as your own personal financial manager. Once you link your bank to the app, Trim analyzes your spending, finds subscriptions you need to cancel, negotiates your Comcast bill, finds you better car insurance, and more. And of course, the app is free! My bet is that it will only take a few days for Trim to put an extra $100 in your pocket. So easy!